Generally, steam traps are provided at suitable places of steam lines or steam appliances for the purpose of automatically exhausting condensed water without passing steam. In the case where such steam traps do not operate normally, there will occur a serious trouble in the activities of steam appliances by failure of steam transportation or by occurrence of steam loss. More particularly, in the case where the exhaust capacity of steam traps attached to steam appliances is less than the quantity of condensed water, or in the case where the condensed-water exhausting function of steam traps deteriorates or is lost so entirely that the valve opening function thereof can not operate, the condensed water will remain in the entrance piping of the steam traps, so that a phenomenon of water hammer will often appear or the efficiency of the steam appliances will be often lowered to cause breakage in extreme case. On the contrary, in the case where the valve closing function of the steam traps is unsatisfactory, it will be apparent that steam leakage increases to thereby cause inconvenience of lowering of efficiency with the shortage in pressure and quantity of the steam and to thereby cause waste of expensive energy undesirably.
As an example of apparatus for detecting steam leakage at a steam valve such as a steam trap or the like, a steam leakage detector has been disclosed in Japanese Utility Model Unexamined Publication No. 58-187739. The steam leakage detector detects vibration in a valve body of a steam valve from the outside of the steam valve to thereby judge presence of steam leakage. The principle of detection in the steam leakage detector is in that a probe provided at the top end of the detector is brought into contact with the steam valve or the like to be detected so that vibration generated in the probe is converted into an electric signal by an ultrasonic microphone using a piezoelectric element, and then the electric signal is amplified and led to a display unit or a speaker to drive the display unit or the speaker.
According to this prior art apparatus, deflection of an indication pointer actuated by the vibration detected by the probe is read or sound from the speaker is listen to recognize the level of vibration, and hence the presence and degree of steam leakage. However, the apparatus has a disadvantage in that steam leakage can not be grasped quantitatively. This is because vibration generated in a valve, such as a steam trap or the like, varies widely with various factors, such as for example the structure and size of the valve, the ratio of steam to condensed water, and the like, though the deflection of the indication pointer or the output of the speaker is proportional to the vibration detected by the probe.